As the world's standard crude oil reserves are exhausted, and the continued demand for oil causes oil prices to rise, oil producers are trying to increase their output of hydrocarbons from bituminous ore, oil sands, tar sands, and heavy oil deposits. These materials are often found in naturally occurring mixtures of sand or clay. Because of the high viscosity of bituminous ore, oil sands, oil shale, tar sands, and heavy oil, the drilling and refinement methods used in extracting standard crude oil are typically not available. Therefore, recovery of oil from these deposits requires heating to separate hydrocarbons from other geological materials and to preserve hydrocarbons at temperatures at which they will flow. Steam is typically used to provide this heat, although electric and radio frequency heating is sometimes employed. The heating and processing can take place in-situ, or in another location after strip mining the deposits.
During in-situ processing, it is difficult to sense the real-time conditions in the deposit and the well bore. Uncertainty often exists about whether the hydrocarbons are indeed flowing. Valuable time and heat energy are wasted in unsuccessful attempts at in-situ processing when low formation permeability conditions prevent diffusion of steam and limit heating, or when steam and heat move away from a zone that is targeted for heating through formation fractures or through high permeability materials.
“Well logging” may be used to check and record subsurface conditions. Such well logging involves an examination of core samples, and moving sensors up or down the well bores. Sensors are used to measure, for example, electrical resistance, acoustic properties, natural radioactivity, density of the formation surrounding the well, and the like. However, these measurements do not produce a near real-time picture of conditions in the formation. They produce only a static and partial picture of such conditions.